Sure, here is an optimal plan to solve the problem:

1. Robot1 picks up ball1 with its left gripper in room1.
2. Robot1 picks up ball2 with its right gripper in room1.
3. Robot1 moves from room1 to room4.
4. Robot1 drops ball2 in room4 with its right gripper.
5. Robot1 moves from room4 to room5.
6. Robot1 drops ball1 in room5 with its left gripper.

This plan ensures that both balls are moved to their respective rooms in the most efficient way possible.